WO2019053504A1

WO2019053504A1 - Method and apparatus for deep marking metallic materials with a movable nozzle for the emission of gas

Info

Publication number: WO2019053504A1
Application number: PCT/IB2018/001081
Authority: WO
Inventors: Maurizio Cucchi
Original assignee: M-Pix Srl
Priority date: 2017-09-15
Filing date: 2018-09-11
Publication date: 2019-03-21
Also published as: EP3681666A1; IT201700103664A1; EP3681666B1

Abstract

The invention is directed to an apparatus for deep marking of solid materials, which apparatus comprises: a scan head laser; a nozzle for the emission of a gas, wherein the nozzle has rectangular section, wherein the longer side of the rectangle entirely covers the breath of the marking along y axis; an engine connected with the nozzle, which engine is capable of moving the nozzle along the x axis synchronously with the movement of the laser beam. In a preferred embodiment, the distance d between laser beam and nozzle is comprised between 1 mm and 50 mm, and the nozzle is inclined with respect to the plane of the solid material of an angle a comprised between 10° and 70. The invention also concerns a process for deep marking a material, with the use of the above defined apparatus. The marking obtained on the material has a breath comprised between 5 mm and 100 mm and a length comprised between 10 mm and 500 mm, and a depth comprised between 0.1 mm and 1.2 mm. Preferably, the material is a metallic material.

Description

METHOD AND APPRATUS FOR DEEP MARKING METALLIC MATERIALS WITH A MOVABLE NOZZLE FOR THE EMISSION OF GAS

[0001]. The present invention is directed to a laser resonator capable of deep marking metallic materials, and to a method for deep marking metallic materials by the use of said resonator.

[0002]. Marking of materials is one of the most prominent field of use of laser resonators. By marking it is possible to add to a product a serial number, expiry or production date, bar codes, alphanumeric codes, etc..

[0003]. Marking can be performed by several methods, such as blackening, decolorizing or changing of color of a material, physical modification of the superficial finish of the material, controlled modification of the material surface by melting, or creation of a groove on the material surface. The present invention concerns the latter method, i.e. the use of a laser resonator for creating a groove deep enough to guarantee reading of the marking even after painting or, in any case, covering of the treated surface by a siding or coating, or a deep groove which is not conveniently obtained by other laser applications.

[0004]. Marking can be operated on any material presenting a solid/liquid/ vapor transition, necessary for punctual fusion/vaporization of the material under the effect of the laser beam. In a preferred embodiment, materials used in the present invention are metallic materials, i.e. metals or metal alloys.

[0005]. Although, as above stated, laser resonators find widespread use in the field of marking, deep marking is usually performed by using mechanical marking means, since in this case laser marking tends to be no longer visible after coating or after other superficial finish. In fact, molten metal does not vaporize by laser beam, and if it is not removed, solidifies again; thus, marking takes place by change of color or by a variation of the superficial state.

[0006]. In the past, laser resonators have been developed which were able to deep mark thanks to the presence of a gas flux coaxial with the laser beam. In this way the material, once molten, is removed by the gas flux and a more or less deep groove is formed in the sheet of material.

[0007]. The limit of this technology is that the use of a gas flux coaxial with the laser beam makes it impossible the use of a scan head laser. A scan head laser is constituted by a fixed scan head, wherein the movement of the laser beam is obtained by a system of mirrors which is placed within the head. The absence of movement of the head results in a high speed of movement of the laser beam, and, consequently, much higher production rates. Thus, the use of a scan head laser would render deep laser marking cheaper when compared to conventional deep marking methods (e.g. hemming, mill finishing, abrasion marking).

[0008]. The present invention is directed to a laser resonator comprising a scan head and capable of producing a deep marking on a material to be marked. Thus, the marking process according to the present invention makes use of a fixed head laser and a fixed, preferably plane, sheet. The movement of the laser beam is obtained by the use of a scan head.

[0009]. In particular, the present invention is directed to a laser resonator comprising: i. a scan head laser; ii. a nozzle for the emission of a gas, wherein the nozzle has rectangular section, wherein the longer side of the rectangle entirely covers the breath of marking along y axis, i.e. the length of the longer side of the rectangle is equal to or larger than the breath of the marking in y direction; iii. an engine connected to the nozzle, which engine is capable of moving the nozzle along the x axis synchronously with the movement of the laser beam.

[0010]. In this way, it is possible to limit the movement of the nozzle to only one of the two directions of movement of the laser beam, making it possible for the nozzle to follow the laser beam, still allowing the scan head laser to work at the maximum speed.

[0011]. In particular, the size of deep marking accordingly to the invention, can vary in a very wide range, for example, in y direction (breath), marking can have a size comprised between 5 mm and up to 100 mm. Preferably, the minimum size is of at least 10 mm, more preferably of at least 15 mm or at least 20 mm. The maximum size is preferably not larger than 60 mm, more preferably not larger than 50 mm or not larger than 40 mm. The length of marking (x direction) can as well vary within a broad range, in particular, the minimum length is normally of at least 10 mm, preferably at least 30 mm, more preferably at least 50 mm. The maximum length is preferably not more than 500 mm, more preferably not more than 300 mm.

[0012]. Concerning depth of marking, i.e. the depth of material removed by the laser beam, it can vary between 0.1 mm and 1.2 mm.

[0013]. The maximum breath of marking influences the size of the longer side of the nozzle to be used in combination with the scan head laser, while the length of marking influences the focal distance, thus the distance between the scan head laser and the sheet to be marked.

[0014]. In a preferred embodiment, the distance between the head of the laser and the sheet is preferably comprised between 50 and 600 mm, more preferably between 100 and 500 mm, depending on the size of the marking to be performed.

[0015]. Concerning the gas used for removing molten material, it is possible to use all gasses commonly used for this purpose, such as air, nitrogen, noble gasses (neon, argon and helium). For economic reasons, it is normally used air as the gas. [0016]. Gas pressure depends on the size of the nozzle and has to guarantee a speed of exit from the nozzle sufficient to remove molten material. Normally, a pressure of at least 3 bar, preferably of at least 4 bar, allows the achievement of the desired result.

[0017]. Figure 1 shows a perspective view of the laser according to the invention. X and Y are the axes along which the laser beam moves. As shown in fig. 1, the breath of the nozzle is such as to cover the entire breath of marking. Thus, as above defined for the size of marking in y direction, the size of the longer side of the nozzle is comprised between 5 mm and up to 100 mm, preferably the minimum size is of at least 10 mm, more preferably of at least 15 mm, or at least 20 mm. The maximum size is preferably not larger than 60 mm, more preferably not larger than 50 mm or not larger than 40 mm.

[0018]. Fig, 2 shows a lateral view of the laser according to the invention. With d it is indicated the distance along x axis between laser beam and nozzle, with h the distance between the plane of the solid material and the nozzle, while a indicates the incline of the nozzle with respect to the plane of the solid material.

[0019]. The nozzle has an incline a with respect the plane of the sheet so that the flux be incident to the marking. However, the value of the incline a can vary in a very broad range for example comprised between 10° and 70°, more preferably between 10° and 50°, even more preferably between 15° and 45°. In a preferred embodiment, a is comprised between about 15° and 30°.

[0020]. The distance d of the nozzle from the laser beam can vary depending on different factors, amongst which the heigth h of the nozzle from the plane of the sheet, the incline a of the nozzle and the speed of gas exiting the nozzle. Preferably distance d is comprised between 1 mm and 50 mm, more preferably between 2 mm and 30 mm, or between 3 mm and 20 mm. Distance d is maintained within the desired range by synchronizing the movement of the engine connected to the nozzle with the movement of the mirror within the head of the scan laser which causes the movement of the laser beam in x direction. However, it is important to note that the movement of the laser beam is much quicker than the movement of the nozzle, and it is possible for the laser beam to move backwards during incision of letters or numbers. In this case, the movement of the nozzle will be about equal to the "average" movement of the nozzle, and consequently the distance of the nozzle will vary of a few millimeters when compared to the predetermined average distance.

[0021]. Concerning height h of the nozzle from the plane of the metallic material, it is preferably comprised between a minimum of 1 mm and a maximum of 50 mm. If the height is lower than 1 mm, there is the risks of bearing phenomena between sheet and nozzle, which can damage the precision of the mechanism. If the height is higher than 50 mm the flux of gas might be too far from the molten material and, as a consequence, the apparatus becomes less effective. When the nozzle has an incline a comprised between 30° and 60°, a preferred distance from the plane of the sheet is comprised between 2 mm and 10 mm.

[0022]. Concerning the laser used in the present invention, it is not particularly limited, and in general any type of laser capable of melting the material to be marked can be used, Examples of lasers particularly useful in the present invention are pulsed lasers, having a duration of the pulse comprised between 0.01 ms and 100 ms, preferably between 0.05 ms and 50 ms, even more preferably between 0.1 ms and 20 ms. The energy of each individual pulse is preferably higher than 0.1 J, more preferably comprised between 0.1 and 30 J. The average of the laser can also vary in a wide range and is preferably comprised between 20 and 1000 W. Concerning wavelength of the laser beam, it can vary in a broad range and it is preferably comprised between 0.8 μιη and 11 μιη, or between 1 μιη and 10 μιη.

Claims

1. Apparatus for deep marking of solid materials, which apparatus comprises:

a. a scan head laser;

b. a nozzle for the emission of a gas, wherein the nozzle has rectangular section,

wherein the longer side of the rectangle entirely covers the breath of the marking along y axis;

c. an engine connected with the nozzle, which engine is capable of moving the nozzle along the x axis synchronously with the movement of the laser beam.

2. Apparatus according to claim 1, wherein the distance d between laser beam and nozzle is comprised between 1 mm and 50 mm.

3. Apparatus according to claims 1-2, wherein the nozzle is inclined with respect to the plane of the solid material of an angle a comprised between 10° and 70°.

4. Apparatus according to claims 1-3, wherein the pressure of the gas upstream the nozzle is equal to or higher than 3 bar.

5. Apparatus according to claims 1-4, wherein the laser is a pulsed laser, having a wavelength comprised between 0.8 and 11 μιη.

6. Apparatus according to claim 5, wherein the duration of the pulse is comprised between 0.01 and 100 ms, and the energy of each pulse is comprised between 0.1 and 30 J.

7. Process for deep marking a material, characterized by the use of an apparatus according to claims 1-6.

8. Process according to claim 7, wherein the marking obtained on the material has a breath comprised between 5 mm and 100 mm and a length comprised between 10 mm and 500 mm.

9. Process according to claim 8, wherein the solid material is a sheet.

10. Process according to claim 9, wherein the sheet is a plane sheet.

11. Process according to claims 7-10, wherein the mark has a depth comprised between 0.1 mm and 1.2 mm.

12. Process according to claims 7-9, wherein the material is a metallic material.